1. Field of the Invention
The present invention relates generally to bandsaw machines having a flexible endless bandsaw blade trained around a plurality of wheels or pulleys to perform cutting operations and, more particularly, pertains to a guiding apparatus for holding and guiding the bandsaw blade.
2. Description of the Prior Art
As is well-known, bandsaw machines include a flexible endless bandsaw blade which is trained around a plurality (usually a pair) of wheels or pulleys, one of which is power driven to drive the bandsaw blade in order to perform cutting operations. One of the stretches of the bandsaw blade trained around the wheels is slidably held or guided by a pair of guide means at the cutting zone where cutting operations are to be made so that the bandsaw blade can cut into workpieces without sideward motion and with reduced vibrations. In horizontal bandsaw machines, the bandsaw blade is held by the guide means in a saw head assembly which is so arranged as to be lowered toward workpieces to be cut, and thus the bandsaw blade is fed into the workpieces to cut the same when the saw head assembly is lowered. Also, in vertical bandsaw machines, the bandsaw blade is held vertical at the cutting zone by the guide means, and in cutting operations workpieces to be cut are fed manually or by power into the bandsaw blade being driven around the wheels. Thus, in bandsaw machines, the bandsaw guide means has to hold the bandsaw blade not only against its sideward motion but also against the feeding force with which the bandsaw blade is fed into the workpiece to be cut or vice versa. For these purposes, each of the guide means of the bandsaw machines comprises a pair of guide members for holding the sides of the bandsaw blade against its sideward motion and a back-up guide member for holding the back edge of the bandsaw blade against the feeding force.
Heretofore, in order to hold the bandsaw blade against the feeding force, wheel-like roller members or otherwise rotatable thrust bearing members have been applied to the back blade edge. However, the bandsaw machines have conventionally suffered from serious disadvantages as to holding the bandsaw blade against the feeding force especially when cutting difficult-to-cut materials or workpieces such as stainless steels, tool steels and super-alloys.
One of the major disadvantages of the conventional bandsaw guide means has been the fact that the back-up guide member is unable to sufficiently overcome the feeding force in several respects especially when cutting the difficult-to-cut materials. The roller-type back-up guide member of the conventional bandsaw guide means cannot sufficiently hold the bandsaw blade against the feeding force, since it keeps in contact with the back edge of the bandsaw blade only by a small point-like area. The back-up guide member of the thrust bearing type cannot hold the bandsaw blade against a large feeding force necessary especially to cut the difficult-to-cut materials, since it is subjected to a thrust load axially from the bandsaw blade. Also, any of the back-up guide members of the conventional bandsaw guide means have experienced premature wear and damage, since the roller-type back-up guide member will be cut into by concentrated load caused by the back edge of the bandsaw blade and the thrust bearing guide member is subjected to sliding friction of the back edge of the same.
Another but very serious disadvantage with the conventional bandsaw guide means has been that the back-up guide member is unable to resiliently respond to reactions or shocks occurring during cutting operations especially when the bandsaw blade is being worked with a large feeding force. As a matter of actual fact, the bandsaw blade is not evenly or uniformly formed with teeth and has inevitably irregularly higher teeth which will cut into the workpiece too deeply and will be liable to break. Also, materials to be cut will often contain irregularly hard portions into which the teeth of the bandsaw blade cannot cut at a predetermined feeding rate without breaking. For these reasons, it is desired that the back-up guide member can resiliently respond to reactions or shocks occurring during cutting operations so as to enable the bandsaw blade to slightly move or bend back in the direction away from the workpiece to be cut or stop cutting into the workpiece. The conventional back-up guide members have been fixedly mounted in the bandsaw guide means in such a manner as to compel the bandsaw blade to work at any conditions with a predetermined feeding force, and as the result the bandsaw blade will be liable to premature wear and breakage especially when cutting difficult-to-cut materials with a larger feeding force.
Recently, there has been an increased requirement to perform cutting operations with a large feeding force to cut difficult-to-cut materials in many industries, and for this purpose it has been strongly desired to obviate the above-described disadvantages with the conventional bandsaw machines.